This invention relates to a sealed multi-row roller bearing device for rolling mills.
In modern high speed rolling mills, a large amount of cooling water is fed for shape control of the rolls in order to secure the sheet thickness accuracy of products. In bearings used as roll neck bearings for such rolling mills, the environment around the bearing box in which the bearing is housed is far more degraded than in conventional equipment, so that some sealing measures or other are required.
As for sealed bearing devices for rolling mill roller necks in which sealing measures of this type are taken, one shown in FIGS. 1 and 2 of Japanese Patent Application Disclosure No. 22648/1980 has been in use these years. A bearing 1 which bears a roll neck 8 inside a bearing box 7 is a 4-row conical roller bearing, wherein, at the opposite ends of the bearing, the outer ends of inner races 2 are axially extended to form inner race extension annular portions 2a, while seal retainer rings 4 are socket-and-spigot-wise removably fitted to the outer end surfaces of outer races 3, so that seal bodies 5 of rubber held in the seal retainer rings 4 are slidably contacted with the outer peripheral surfaces of said inner race extension annular portions 2a, the opposite ends of the bearing 1 being thus sealed by contact type sealing mechanisms 6. Thus, in this bearing 1, not only by a conventional sealing mechanism having contact type seal bodies 9a, 9b, and 9c installed between it and the roll neck 8 at the opposite ends of the bearing box 7, but also in the bearing box, sealing is effected at the opposite ends of the bearing 1 in the bearing box 7, so that entry of cooling water into the bearing 1 is prevented by the two-stage barrier. Further, leakage of grease fed to the bearing 1 is also prevented, so that there is no need to feed grease each time the rolls are exchanged, and hence the consumption of grease can be reduced.
However, modern rolling mills are operated at high speed, and if the aforesaid conventional bearing sealing mechanism is used in such rolling mills, the inner pressure of the bearing is increased by the rotation of the bearing and the gas in the bearing develops volumetric expansion due to heating by rotation. However, since the seal bodies 5 are in slide contact with the outer peripheral surfaces of the extension annular portions 2a of the inner races 2, passage of gas between the interior and exterior of the bearing cannot be smoothly effected, and in the cycle of the bearing, "high speed rotation.fwdarw.reduced speed rotation.fwdarw.stoppage," a violent inhaling action takes place, entailing entry of cooling water into the bearing or leakage of the grease in the bearing. Further, since the rotative speed of the roll neck is far greater than the permissible peripheral speed of the rubber forming the seal bodies 5, the slide portions of the seal bodies 5 tend to wear out or the seal bodies 5 are hardened by the heat of friction, suffering elasticity degradation, which rapidly lowers the sealing performance. Particularly because seal bodies 9a, 9b, and 9c are disposed at the opposite ends of the bearing box 7, the seal bodies 5 can hardly be cooled by cooling water and hence the heat of friction increases to accelerate elasticity degradation.
Furthermore, a sealing mechanism to be applied to a rolling mill which employs a roll shift mechanism and a strong bender, such as a modern rolling mill, must have the ability to cope with a large amount of deflection of the axis in view of a large amount of bending of the rolls. However, the aforesaid contact type sealing mechanism cannot satisfactorily cope with such deflection of the axis, and in this respect, too, there is a problem in the sealing performance.
Further, in the aforesaid bearing 1, as the diameter of the bearing is increased, the cross-sectional shape of the seal bodies 5 must be similarly enlarged; if not, predetermined sealing performance could not be obtained. Thus, the width of the sealing mechanism increases and hence the effective width of the bearing correspondingly, reduces, thereby reducing the load carrying capacity. Further, since the seal retainer rings 4 are simply socket-spigot-wise removably fitted to the outer races 3, there is the danger of their slipping off the outer races when the bearing is attached to and detached form the roll neck, thus resulting in damaging the seal bodies.